I'll be 100% honest with you: the best way to identify sweet cherries is to find out when Bing cherries are picked in your area. Bing is the "benchmark" for US cherries, with ripening times always being given as x weeks before and after Bing. In fact the largest one at the bottom of the first picture could well be a Bing: it's the most popular sweet cherry cultivar in the US and ripening time could be about right as well.
